A percussion or impact drill can have a drill chuck mounted on the drill spindle for rotation or turning therewith. The drill spindle can have a longitudinal or axial passage through which the impact force or action of a central ram shaft is imparted to a drill bit which is held in the drill chuck between centrically adjustable chuck jaws.
In such apparatus the ram or hammer shaft is axially guided in the hollow drill spindle, and coupling elements are provided for connecting the drill chuck to the drill spindle. The coupling elements can be arranged in retainers of the drill spindle and/or of the chuck body of the drill chuck.
In practice a drill chuck of this type is known which has a coupling ring which is guided in such a way that it cannot be shifted in axial direction, but is rotatably guided at the chuck body. The coupling ring can be fixed in respective positions in conformity with its rotation, and holds the respective coupling elements so that these are positively engaged in coupling retainers of the drill spindle. The coupling ring can be rotated into a position corresponding to the disengaged condition of the coupling, and the coupling elements can then move out of the coupling retainers at the drill spindle. The drill chuck can then be removed from the drill spindle by being displaced in axial direction.
In the coupled or engaged condition, the chuck body of the drill chuck is held on the drill spindle in such a way that substantially no axial play is experienced. This means that the coupling retainers in the drill spindle and in the drill chuck body have the same axial dimensions as the coupling elements so that the coupling elements are fixed in an axially directed and positively locking attitude with respect to the coupling retainers.
The coupling ring can be clamped against the chuck body by means of a clamping screw which, in turn, is radially guided in the coupling ring. However, this entails relatively large forces for clamping because the coupling ring also contains the guide retainers for the tensioning key which serves to open or close the drill chuck. The coupling ring, however, must not rotate with respect to the drill body in order to achieve the desired tightening of the drill chuck by means of the chuck key.
However, particularly in the case of percussion drilling, it is often desired that the drill chuck be arranged with a certain play or axial mobility with respect to the drill spindle. This prevents the mass of the drill chuck from intercepting and attenuating impact movements and eliminates negative influences upon the drilling operation.